Production-Ready Technical File: Drawings, Pantone Colour Matching and a Checklist

On a membrane switch or embossed graphic panel project, the lead time to first sample is usually set not by production capacity but by the maturity of the incoming data pack. A production-ready technical file is the set of documents that lets the manufacturer start film output, cutting programs and screen preparation without asking a single clarifying question. In practice most projects start well short of that definition: the DXF exists but the outline is an open polyline, the colour is described as “dark grey”, and nobody stated whether the ZIF tail contacts face up or down. Those three gaps alone are worth two weeks of revision emails. Below is every component of the file, from the mechanical drawing to Pantone colour matching, plus the checklist to tick off before you send anything.

What a production-ready technical file contains

A single PDF is not enough, because different production stations read different data. Cutting needs vector geometry, screen printing needs separated colour layers, assembly needs a cross-section. The minimum set is:

What the mechanical drawing must state

• Closed geometry: the outline and every window must be closed polylines; an open contour cannot be transferred to a cutting die or a laser program.
• One datum corner: dimension all holes from the same datum. Chain dimensioning accumulates error from hole to hole.
• Corner radii: a sharp internal corner is where polyester starts to tear; use R1 or larger wherever the design allows.
• Tail data: exit point, width, bend direction and length. Length must be measured along the routing path in the assembly, not as a straight line.
• Connector detail: ZIF type and pitch (1.0 mm is common), whether contacts face up or down, plus stiffener thickness and position.
• Key data: key centres, active area diameter, and alignment of the metal dome diameter with the printed key area if domes are used.
• Embossing: pillow or rim embossing, height and edge transition, marked key by key.
• Adhesive area: frame width and whether it is continuous. If you target IP65/IP67, the adhesive frame must form an unbroken loop and the tail exit must be sealed separately.

Tolerance chain and thickness budget

Cutting tolerance depends on the method: typically ±0.2 mm for die cutting and ±0.3 mm for laser cutting. Evaluate that figure together with the mating cut-out in the enclosure; when both tolerances stack in the same direction, the assembly clearance can disappear. On the thickness side, a typical six-layer construction lands between 0.9 mm and 1.4 mm. Graphic layers are usually specified as PET at 0.125–0.2 mm or polycarbonate at 0.175–1.0 mm. Adhesive is part of the budget too: 3M 467MP adds roughly 0.05 mm (2 mil) and 468MP roughly 0.13 mm (5 mil). State a target total thickness with a tolerance, otherwise the assembly gap becomes a discovery rather than a specification.

How to specify Pantone colour matching correctly

Colour is the most underestimated line in the file. On membrane switches and graphic panels the artwork is usually printed on the second surface, that is, the reverse of a clear film, so the observer sees the ink through the substrate. A Pantone chip printed on paper will therefore never look identical to the same number on a panel. The correct approach:

• Give the number and the suffix: Solid Coated (C) and Uncoated (U) of the same number look visibly different. “Pantone 300” alone is incomplete information.
• State the surface texture: gloss film and matte/velvet film render the same ink differently; a matte texture diffuses light and reads slightly lighter and cooler.
• Do not forget the backing layer: in second-surface printing, without an opaque white behind the colour, the darker layers underneath will pull the shade down.
• Separate spot from process: corporate colours and solid fields are printed as spot inks; photographic areas and gradients are process printed. Do not mix them in one layer.
• Define the approval method: colour must be approved against a physical reference in a standardised light booth (D50 or D65), not on a screen. That is how metamerism, two samples matching under one light and not another, gets caught.
• Sign off a colour master: once the first sample is approved, that part becomes the reference for later batches and its tolerance, an upper ΔE limit, should be written into the file.

A frequent mistake is quoting RAL codes as a screen-ink reference; RAL is a paint standard. If the main panel colour was defined in RAL, state in the acceptance criteria that an ink equivalent will be matched and that a small deviation is expected.

Daylight and night appearance on backlit panels

One colour description is not enough for backlit panels: the unlit (daylight) and lit (night) appearance must be defined separately. In a dead-front design the icon sits invisibly in the background when the light is off and appears only when illuminated; this requires a low-transmission tint layer over the window, and both the transmission target and the accepted contrast against the surrounding field when unlit must be written down. The LED itself also shifts the perceived hue of the window, so specifying the colour temperature of white LEDs is the shortest way to avoid surprises on yellow and green icons. For life planning, 50,000–100,000 hours is a typical order of magnitude for LEDs.

Artwork preparation rules that get skipped

• Convert all text to outlines; a missing font silently changes letter widths.
• Keep the artwork at 1:1 and aligned to the same datum corner as the mechanical drawing. Centring the graphics by eye shifts icon centres away from key centres.
• Ask about minimum line width and text height early; very fine detail can fill in or break up in screen printing.
• Define windows and transparent areas on a separate layer as closed paths, and state which ink, if any, covers them.
• Leave margin between print and cut line; where print runs into the cut edge, cutting tolerance becomes directly visible.

Pre-release checklist

Work through the following before sending the pack. In our experience the majority of revision rounds trace back to three or four items on this list.

• Are the outline and all windows closed polylines?
• Is the drawing 1:1, in mm, dimensioned from a single datum corner?
• Have cutting tolerance (die ±0.2 mm / laser ±0.3 mm) and assembly clearance been checked together?
• Is the total thickness target and layer order documented?
• Is the graphic layer material and thickness selected (PET 0.125–0.2 mm / PC 0.175–1.0 mm)?
• Are adhesive type and thickness stated (for example 2 mil or 5 mil)?
• Is the surface texture defined as gloss or matte?
• Are all colours given with number plus suffix (C/U)?
• Are the colour approval method and tolerance written down?
• For backlit panels, are lit and unlit appearances described separately?
• Is the key type selected: metal dome (typically 1–5 million cycles) or poly dome (typically 100,000–500,000 cycles)?
• Are the target actuation force and its acceptance tolerance (for example ±20%) stated?
• Are embossing type, height and affected keys marked?
• Was tail length measured along the routing path?
• Are ZIF pitch, contact side orientation and stiffener defined?
• Are matrix/pin order and LED polarity unambiguous in the schematic?
• If an IP target exists, is the adhesive frame continuous and the tail exit resolved?
• Does the filename carry a project code, revision number and date?

Typical mistakes that stretch the revision loop

First, no revision control. If three files named “final” are in circulation, it becomes debatable which data the panel was built from; adding revision and date to the filename is the cheapest quality measure available. Second, dimensions that disagree with the geometry: when the drawing is not to scale and values are typed by hand, production has to decide which one governs. Always send a file where the geometry is correct and the dimension merely describes it. Third, dimensions without tolerances; every untoleranced value falls back to a general acceptance, and a critical hole centre can drift with it. Fourth, a tail that ends up reversed: when contact side orientation is not stated, the tail has to be rotated 180 degrees during assembly, which compromises both the bend radius and the cable route.

A file that closes these items finishes the first-sample dialogue in a single round. Send your drawing and colour data, and Tuşhan Elektronik will review it for manufacturability, mark any missing items and return it together with a quotation.